OS X: If you leave your Mac on at night, but forget to mute your system or turn the volume down, Silencer is a tiny menubar utility that can mute and unmute your Mac's speakers at a specific time every day, whether you mute it before bed and have it automatically restore the volume in the morning, or mute it before you leave for work and unmute it when you get home.

Silencer will set you back $0.99 in the Mac App Store. The developer built the app because he had a cat that liked to curl up on his Macbook Pro at night (which he liked to leave on at night while he rendered video and did file copies and backups), and if he forgot to mute the system, the first email he got in the middle of the night would wake the cat up—and we all know what an irritated, rattled-awake cat will do in the middle of the night while you're sleeping. Still, even if you don't have a cat, the app could be useful for keeping your system quiet without forcing you to turn it off, put it to sleep, or remembering to silence it.